The purpose is to pursue investigations to elucidate and evaluate factors affecting the behavior of peroxisomes in an attempt to understand the biological role of these cytoplasmic organelles. These studies will be performed utilizing the peroxisome proliferative property of certain hypolipidemic compounds, as well as a number of plasticizers, which are potential environmental contaminants. Morphological and biochemical alterations in liver, associated with drug induced peroxisomal proliferatton and the factors that modify these changes will be delineated. Effect of exposure of pregnant mice to these peroxisome proliferators, on the fetal and neonatal mice will also be investigated. Effect of lifetime exposure to selected peroxisome proliferators in rats and mice will be investigated in view of the development of hepatocellular carcinoma in rats and mice treated chronically with nafenopin. The information obtained from these studies should further our knowledge of peroxisomes.